package com.hmdp.utils;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

@Component
public class RedisIdWorker {

    /**
     * 从2025.01.01T00:00:00(UTC)开始的开始时间戳
     */
    private static final long BEGIN_TIMESTAMP = 1735689600L;

    /**
     * 序列号的位数
     */
    private static final int COUNT_BITS = 32;

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    public Long nextId(String keyPrefix) {
        // 1. 生成时间戳
        LocalDateTime now = LocalDateTime.now();
        long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
        long timestamp = nowSecond - BEGIN_TIMESTAMP;
        // 2. 生成序列号
        // 2.1. 获取当前日期, 精确到天
        String date = now.format(DateTimeFormatter.ofPattern("yyyyMMdd"));
        // 2.2. 自增长 // 这里提示自动拆箱可能会导致空指针异常, 实际并不会, 因为如果key不存在会自动创建一个key
        long count = stringRedisTemplate.opsForValue().increment("icr:" + keyPrefix + ":" + date);
        // 3. 拼接并返回
        return timestamp << COUNT_BITS | count;
        // return (timestamp << COUNT_BITS) + count; // 注意加法运算优先级更高
    }
}
